Para-type aromatic polyamide fibers formed of a para-oriented aromatic dicarboxylic acid component and an aromatic diamine component have been widely used for industrial material purposes and functional clothing purposes by taking advantages of such characteristics as high strength, high modulus of elasticity and high heat resistance. In particular, the demand of para-type aromatic polyamide short fibers is being increased in recent years mainly for functional clothing purposes required to have high strength and high heat resistance, such as fireman clothing, protective clothing and safety gloves.
However, para-type aromatic polyamide fibers have high rigidity and are difficult to be imparted with sufficient winding crimping property even though indentation crimping is applied thereto, and thus they become insufficient in bundling property in a spinning process as being combined with the high modulus of elasticity, whereby such a problem arises that handling failure and web breakage are liable to occur due to the bulkiness thereof.
Furthermore, various problems in a spinning process are being elicited that are ascribable to the characteristics inherent to para-type aromatic polyamide, such as formation of scums through fibrillation and generation of static charge due to high orientation and high strength of the fibers.
In view of the problems, an oily agent that has been used for other fibers, such as polyester long fibers and short fibers and polyamide fibers for industrial material purposes, is often applied to the conventional para-type aromatic polyamide fibers, but associated with elicitation of the problems, there arises an increasing demand of a unique oily agent that is dedicated to the characteristics of the para-type aromatic polyamide, and development thereof is being attempted.
For example, JP-A-3-185180 proposes a method of improving antifriction property on the fiber surface (suppressing scums) by applying an ethoxylated alkyl phosphate ester, and JP-A-9-188969 proposes a method of preventing fibers from being dropped in a spinning process by applying an oily agent containing a long-chain alkyl phosphate ester having a particular carbon number, so as to suppress wholly aromatic polyamide fibers from being fibrillated.
However, the ethoxylated alkyl phosphate ester is excellent in antistatic property and antifriction property, but has such a problem that the adhesion property thereof is changed with lapse of time due to the hygroscopic property thereof, which brings about twining on various rollers in a spinning process. The long-chain alkyl phosphate ester having a carbon number of from 18 to 20 is effective for decreasing spinning scums and twining on rollers, but has a problem of insufficient spinning property due to insufficient bundling property of the fibers.
In order to solve the problems, JP-2001-207379 proposes a method of applying an oily agent containing an alkyl phosphate ester having a carbon number of from 14 to 16 and an antistatic agent. According to the method, the bundling property and the antistatic property are improved, and twining on rollers is also reduced, to improve the spinning property, but the antistatic property at a low temperature and a low humidity is still insufficient, which brings about necessity of combination use of another antistatic agent, and thus further improvement is being demanded.
In recent years, a considerably high speed operation is being practiced not only in curding, drawing and roving but also in fine spinning for the purpose of reducing the spinning cost by high productivity, energy saving and high efficiency. In the high-speed spinning, the amount of scums is increased since the amount of fibers passing through a spinning machine is increased in proportion to the speed, whereby such problems arise that not only the frequency of cleaning is increased to deteriorate the operability, but also breakage of thread is caused thereby. In order to solve the problems, JP-A-6-108361 proposes a method of applying an oily agent containing an alkyl phosphate ester potassium salt, paraffin wax and a cationic surfactant, and JP-A-10-183469 proposes a method of applying an oily agent containing at least one compound selected from the group consisting of a compound obtained by blocking at least a part of terminal hydroxyl groups of an ethylene oxide adduct of alkylamine with an alkyl group, an alkenyl group or an acyl group, a neutralized product of the compound with phosphoric acid or a phosphate ester, and a quaternarized product of the compound, and the oily agent also containing a lubricating material. However, these attempts are still insufficient for aromatic polyamide fibers, and further improvement is being demanded.